We will continue research in respiratory mechanics in four projects: 1. Micromechanics of the lung. Photoelectric measurement of the dispersion of visible light passing through lung will be used to estimate the alveolar surface to volume ratio. Distribution of lung expansion during high frequency forced oscillation as seen at the lung surface will be studied by stroboscopic methods. Studies of collateral flow and pulmonary tissue properties by gas compression techniques will be continued. Airway aerodynamics. A model which fits the mouth to body-surface flow transfer function as obtained this past year during forcing at the rib cage surface, will be related to mechanical parameters and the influence of changing these parameters on the measured transfer function will be studied. Also the transfer function during abdominal forcing will be obtained. Chest wall mechanics and respiratory control. Spinal attitude will be measured continuously together with measurements of rib-cage and abdominal body surface displacements to yield a three degrees of freedom description of chest wall volume displacements. The mechanical actions of the diaphragm on the rib cage will be analyzed from pressure-volume descriptions which include partitioning of pleural and abdominal pressure according to maps of the extended area of opposition diaphragm to rib cage obtained by ultra-sonographic techniques. Studies of operational length compensation will be done in unanesthetized goats. Development and evaluation of tests of pulmonary function. The influence of bronchoconstriction and bronchodilation on the reproducible details of forced expiratory flow-volume curves will be studied in human subjects.